DIVA POWER

Especially when it comes to beauty, teenage girls, ages 13 to 19, are a consumer segment mass retailers, including supermarkets, are beginning to covet.This group's spending power, $48 billion annually, is so awesome that Wal-Mart Stores set up a section called Trend Zone to attract teens. Food chains such as Wegmans Food Markets, Rochester, N.Y., also are now stocking funky nail polish in flower